In conventional amine contacting systems, an aqueous solution of dissolved amines is contacted in a counter current manner with a gaseous stream containing CO2 and/or H2S. The gases to be separated react with the solubilized amines at a temperature range of about 30° C. to about 60° C. The “rich” solution of amines reacted with CO2/H2S is then heated with steam stripping to a temperature range of about 110° C. to about 140° C. in order to release the CO2 and/or H2S. In such conventional processing a significant amount of energy is required to heat the entire rich aqueous solution. While feed/product heat exchange for the stripping step is normally utilized, such heat exchangers significantly affect the capital cost of the system, often dictating the maximum amine circulation rate that can be utilized.
U.S. Pat. No. 7,846,240 describes a chilled ammonia based CO2 capture system. CO2 is adsorbed using an ammonia solution or slurry at a temperature below ambient. If a slurry is used, the particles in the slurry correspond to particles of ammonium carbonate and/or bicarbonate that have precipitated in the solution. When a slurry is used, the carbon capture and release mechanism is based on consumption and generation of CO2 as the particles convert between carbonate and bicarbonate forms. In addition to maintaining the ammonia at a below ambient temperature, preventing loss of ammonia in exhausted flue gas is also a concern.
An article by Langeroudi et al. (Journal of Physical Chemistry C, 2009, Vol. 113, pp. 21866-76) describes CO2 solubility experiments performed on aqueous slurry solutions of silica particles including grafted amines. The solubility experiments included exposing the slurry solutions to various partial pressures of CO2 in a static reaction vessel.